Logging from Java app to ELK without need for parsing logs

If you really want to go down that path, the idea would be to use something like an Elasticsearch appender (or this one or this other one) which would ship your logs directly to your ES cluster.

However, I'd advise against it for the same reasons mentioned by @Vineeth Mohan. You'd also need to ask yourself a couple questions, but mainly what would happen if your ES cluster goes down for any reason (OOM, network down, ES upgrade, etc)?

There are many reasons why asynchronicity exists, one of which is robustness of your architecture and most of the time that's much more important than burning a few more CPU cycles on log parsing.

Also note that there is an ongoing discussion about this very subject going on in the official ES discussion forum.

I think it's usually ill-advised to log directly to Elasticsearch from a Log4j/Logback/whatever appender, but I agree that writing Logstash filters to parse a "normal" human-readable Java log is a bad idea too. I use https://github.com/logstash/log4j-jsonevent-layout everywhere I can to have Log4j's regular file appenders produce JSON logs that don't require any further parsing by Logstash.

There is also https://github.com/elastic/java-ecs-logging which provides a layout for log4j, log4j2 and Logback. It's quite efficient and the Filebeat configuration is very minimal.

Disclaimer: I'm the author of this library.